﻿/*
 *   _____                                ______
 *  /_   /  ____  ____  ____  _________  / __/ /_
 *    / /  / __ \/ __ \/ __ \/ ___/ __ \/ /_/ __/
 *   / /__/ /_/ / / / / /_/ /\_ \/ /_/ / __/ /_
 *  /____/\____/_/ /_/\__  /____/\____/_/  \__/
 *                   /____/
 *
 * Authors:
 *   钟峰(Popeye Zhong) <zongsoft@gmail.com>
 *
 * Copyright (C) 2010-2020 Zongsoft Studio <http://www.zongsoft.com>
 *
 * This file is part of Zongsoft.Data library.
 *
 * The Zongsoft.Data is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3.0 of the License,
 * or (at your option) any later version.
 *
 * The Zongsoft.Data is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the Zongsoft.Data library. If not, see <http://www.gnu.org/licenses/>.
 */

using System;
using System.Collections.Generic;

using Zongsoft.Data.Metadata;

namespace Zongsoft.Data.Common.Expressions
{
	/// <summary>
	/// 表示表标识的表达式。
	/// </summary>
	public class TableIdentifier : Expression, IIdentifier, ISource, IEquatable<TableIdentifier>
	{
		#region 构造函数
		public TableIdentifier(IDataEntity entity, string alias = null)
		{
			this.Entity = entity ?? throw new ArgumentNullException(nameof(entity));
			this.Alias = alias;
			this.Name = DataEntityExtension.GetTableName(entity);
		}

		public TableIdentifier(TableDefinition table, string alias = null)
		{
			this.Table = table ?? throw new ArgumentNullException(nameof(table));
			this.Alias = alias;
			this.Name = table.Name;
		}
		#endregion

		#region 公共属性
		/// <summary>
		/// 获取对应的表元数据元素，与<see cref="Table"/>属性互斥。
		/// </summary>
		public IDataEntity Entity { get; }

		/// <summary>
		/// 获取对应的表定义，与<see cref="Entity"/>属性互斥。
		/// </summary>
		public TableDefinition Table { get; }

		/// <summary>
		/// 获取表的物理名称（即数据库中表的名称）。
		/// </summary>
		public string Name { get; }

		/// <summary>
		/// 获取或设置表标识的别名。
		/// </summary>
		public string Alias { get; set; }

		/// <summary>
		/// 获取一个值，指示当前表标识是否指向一个临时表。
		/// </summary>
		public bool IsTemporary
		{
			get => this.Table != null && this.Table.IsTemporary;
		}
		#endregion

		#region 公共方法
		/// <summary>
		/// 创建一个关联当前表的字段标识。
		/// </summary>
		/// <param name="name">指定的字段名称。</param>
		/// <param name="alias">指定的字段别名。</param>
		/// <returns>返回创建成功的字段标识。</returns>
		public FieldIdentifier CreateField(string name, string alias = null)
		{
			return new FieldIdentifier(this, name, alias);
		}

		public FieldIdentifier CreateField(IDataEntityProperty property)
		{
			return new FieldIdentifier(this, property.GetFieldName(out var alias), alias)
			{
				Token = new DataEntityPropertyToken(property)
			};
		}

		public FieldIdentifier CreateField(IDataEntitySimplexProperty property, string alias = null)
		{
			if(string.IsNullOrEmpty(property.Alias))
				return new FieldIdentifier(this, property.Name, alias)
				{
					Token = new DataEntityPropertyToken(property)
				};
			else
				return new FieldIdentifier(this, property.Alias, alias)
				{
					Token = new DataEntityPropertyToken(property)
				};
		}

		public FieldIdentifier CreateField(DataEntityPropertyToken token, string alias = null)
		{
			var simplex = token.Property.IsSimplex ?
				(IDataEntitySimplexProperty)token.Property :
				throw new ArgumentException($"The specified '{token.Property.Name}' property is not a simplex property, so you cannot create a field identifier for it.");

			if(string.IsNullOrEmpty(simplex.Alias))
				return new FieldIdentifier(this, simplex.Name, alias) { Token = token };
			else
				return new FieldIdentifier(this, simplex.Alias, alias) { Token = token };
		}
		#endregion

		#region 重写方法
		public bool Equals(TableIdentifier other)
		{
			if(other == null)
				return false;

			return this.IsTemporary == other.IsTemporary &&
			       string.Equals(this.Name, other.Name, StringComparison.OrdinalIgnoreCase) &&
			       string.Equals(this.Alias, other.Alias, StringComparison.OrdinalIgnoreCase);
		}

		public override bool Equals(object obj)
		{
			if(obj == null || obj.GetType() != this.GetType())
				return false;

			return this.Equals((TableIdentifier)obj);
		}

		public override int GetHashCode()
		{
			var alias = this.Alias;

			if(string.IsNullOrEmpty(alias))
				return this.Name.ToUpperInvariant().GetHashCode();
			else
				return this.Name.ToUpperInvariant().GetHashCode() ^ alias.ToUpperInvariant().GetHashCode();
		}

		public override string ToString()
		{
			if(string.IsNullOrEmpty(this.Alias))
				return (this.IsTemporary ? "#" : string.Empty) + this.Name;
			else
				return (this.IsTemporary ? "#" : string.Empty) + this.Name + " AS " + this.Alias;
		}
		#endregion
	}
}
